Anode heat dissipating assembly for electron discharge tubes



w. 1.. VROOM 3,229,140

ANODE HEAT DISSIPATING ASSEMBLY FOR ELECTRON DISCHARGE TUBES Jan. 11, 1966 Filed Dec. 26, 1961 FIG. 2

FIG. I

United States Patent C) 3,229,140 ANGDE HEAT DTSSTPATING ASSEMBLY F03 ELEQTRGN DISQHARGE TUBES William L. Vroom, Newark, NJ, assignor'to General Signal Corporation, a corporation of New York Filed Dec. 26, 1961, Ser. No. 161,837

6 @Claims. (it. 3l342) The present invention relates to discharge tubes of the grid control type, and more particularly to an improved anode assembly therefor.

In grid control gas tubes it is necessary that the anode to grid shield spacing be quite small. This close spacing assists in reducing gas clean up, reducing the deionization time, and increasing the voltage the tube can control. The anode is heated by electron bombardment and PR losses during conduction, principally at the center of the anode where the discharge is concentrated. This localized heating tends to cause the anode to warp thereby destroying the spacing between the anode and the grid shield, and hence, the desirable tube characteristics are destroyed. The localized heating also provokes electron emission from the anode which destroys the control ability of the tube.

Heretofore, it was customary, in the construction of tubes of this type, to connect each anode lead by an individual support fin. However, as the center of the anode heated and expanded, the lower ends of the fins were forced apart which applied a stress to the anode lead weld and the glass press. This tended to cause the Weld to break and/or the glass press to crack.

One of the objects of the present invention is to provide an improved anode assembly for an electron discharge tube.

Another object of this invention is to provide a support structure for the anode of a grid controlled discharge tube which reduces warping of the anode when it is heated so that accurate spacing may be maintained between the anode and the grid shield.

Another object of this invention is to provide an improved anode support assembly which present-s a large radiating area for the dissipation of heat from the anode.

A further object of this invention is to provide an improved anode mounting structure which provides a large contact area at the center portion of the anode to radiate heat therefrom.

A still further object of this invention is to provide an improved anode assembly which provides good electrical and thermal conduction, mechanical strength, and reduces local heating by conducting the heat to cooler parts of the anode and to its support where it is dissipated by radiation.

A still further object of this invention is to provide an improved anode assembly which is so constructed and configurated that the anode can be induction heated without overheating the radiating fins.

Other objects of this invention will become apparent from the specification, the drawing and the appended claims.

In the drawing:

FIGURE 1 is a sectional elevation of a tube embodying the present invention;

FIGURE 2 is a cross-sectional view taken along lines 22 of FIGURE 1 and looking in the direction of the arrows;

FIGURE 3 illustrates a plane view of a blank used in making one part of the anode support, and an end elevation of this blank bent to its required configuration; and

FIGURE 4 illustrates a plane view of a blank used in making another part of the anode support, and a section of this blank bent to its required configuration.

Patented Jan. ll, 1966 Generally speaking, and without attempting to limit the scope of the present invention, the anode, which is preferably a thin circular metallic sheet having an upturned peripheral flange, is supported by a plurality of radially extending sheet metal fins which are arranged in a generally Y shaped configuration, with the fins being attached on the upper face of the anode and spaced angularly to have their extreme edges approximately one hundred and twenty degrees apart. These fins are sand blasted to facilitate radiation cooling, and are joined to the upper face of the anode by many closely spaced spot welds to provide good electric and thermal conduction and mechanical strength. The anode leads which support the anode spaced from the grid shield are welded to one of the metal fins at a cool part of the fin spaced from the anode.

Because the center of the anode is normally the hottest part, a support assembly according to the present invention, which provides the greatest contact area at the center of the anode, dissipates this concentrated heat more effectively. During manufacture, the anode of the tube is heated to remove trapped gases. This causes the anode to expand, stretching the outer edge of cooler metal. Upon cooling, the center of the anode contracts, but the edge, having been cold formed, is now too great in perimeter which heretofore tended to warp the anode plate. Thus, heretofore two points one hundred and eighty degrees apart on the anode tended to bend upwardly, while two similar points of the anode which are ninety degrees displaced from the first two points tended to bend downwardly. The three radially extending fins, in accordance with the present invention, tend to suppress these undulations, and warping is reduced to an absolute minimum, while at the same time permitting simplicity of manufacture and an eflicient heat radiating area.

Referring to the drawing by numerals of reference, a tube generally referred to at 10 is provided with a conventional cylindrical cathode assembly 12 which is provided adjacent its bottom and top with reinforcing strips 14. The cathode assembly 12 is rigidly supported in a glass envelope 16 of the usual type by two stiff bifurcated uprights 18 which are welded at their upper ends to the bottom edge of the assembly 12 and its associated reinforcing strip 14. The lower end of the strip 18 is welded to a metal collar 20 which is mounted on a glass reentrant stem 22 of the tube envelope 16. The collar 29 is crimped tightly on the glass stem 22 in a conventional manner. The cathode assembly 12 is also provided with connecting rods 24 which are welded at their upper ends to the bottom of the cathode assembly 12 and are bent and anchored in the re-entrant stem 22 in a conventional manner. The connecting rods 24 may be connected to suitable leads.

A grid assembly 25, which is comprised of a circular sheet metal piece, has a central dischage opening over which a plurality of spaced grid bars 26 are fastened in a conventional manner. The grid assembly is rigidly supported and spaced axially of the upper end of the cathode assembly 12 by insulating assemblies 225, which are comprised of ceramic members having axially spaced recesses, for insulating the grid 25 from the cathode assembly 12. A grid connector 34} is attached, as by welding to the grid assembly 25, and extends downwardly in the envelope 16, for connection at its lower end in a conventional manner to a rod 32 that extends into the glass press 22 and is connected to a wire for connection to an external source. Spaced axially above the grid assembly 25 and rigidly supported therefrom by a plurality of ceramic insulating assembly 33, is a grid shield assembly 35. The grid shield assembly 35 is comprised of a circular sheet metal outer portion 36 having a peripheral up-turned flange 38, and a circular inner portion 40 having peripheral upturned flange 42. The circular inner can 449 is so dimensioned that it nests in the outer can 36 so that the upper edges of the peripheral flanges 42 and 35 are substantially coextensive and engaging each other.

An anode 44, which is a thin circular sheet of nickel, approximately thirty thousandths of an inch thick for example, and which formed with an up-turned peripheral flange 45, is spaced from the upper edge of the grid shield assembly 35 a predetermined distance such as two to three millimeters, for example. The anode 44 is rigidly supported in this spaced relationship by a pair of anode leads 46 that are securely fastened in a glass anode press 48 of the glass envelope 16. The upper ends of the leads are connected in the usual manner to wires 49 for connection to an external source. The lower ends of leads 46 are attached as by welding to the upper portion of a generally rectangular heat radiating fin 50. The heat radiating fin Sil the surface of which extends in a plane normal to the face of the anode 44 when in place, is attached to the upper surface of the anode 44 by closely spaced spot welds, such as are referred to at 53 of FIGURE 2.

The fin 50 is formed from a single sheet metal blank (FIGURE 4), which is formed to have spaced substantially parallel bends referred to by dashed lines 54. When the blank is bent, the fin 50 has a central fin portion 55, and angularly extending end fin portions 56. The end portions 56 each extend outwardly to form an inside angle of approximately one hundred and thirtyfive degrees with the central portion 55. The length of the central fin portion 55 and the end fin portion 56 are substantially equal. A lower part of the central fin portion 55 is bent upwardly normal to the plane of the central portion 55 to form a flange 57. Each end fin portion 56 is also bent along a lower part to form a flange 58. The flange 57 is formed with opposite edges 60 which extend at an angle to abut similarly configurated opposing edges 61 of the flanges 58 when the blank is formed to constitute the entire fin 50. A generally rectangular fin referred to at 62, is formed of a thin sheet metal blank having a side portion, which is bent at approximately an angle of ninety degrees to the plane of the fin 62 to form one side flange 64. The fin 62 also has a lower portion which is bent at an angle of ninety degrees to the plane of the fin 62 only in the opposite direction to the flange 64 to form a bottom flange 66. The bottom flange 66 extends at right angles to the flange 64.

The fin 62 is attached to the center fin portion 55 of the fin 50 by its side flange 64 by spot welding at closely spaced points to form good contact therewith. The fin 62 is so positioned that it extends normal to the plane of the center fin portion 55 so that its outer edge 67 is angularly spaced from outer edges 69 of the fin 59 one hundred twenty degrees. It is also positioned so that its flange 66 lies in the same plane as the flanges 57 and 58 of the fin 50. The bottom flange 66 of the fin 62, and the flanges 57 and 58 of the fin 50 is attached to the upper face of the anode 44 by closely spaced spot welds such as are referred to at 68 and 53. The fin 62 is positionally attached so that the bend at the flange 64 is approximately equidistant from the spaced bends of the center fin portion 55. The entire fin assembly which is comprised as the fin 50 and the fin 62, is so positioned on the anode 44 that the juncture 70 of the fin 62 and the center fin portion 55 is substantially at the center of the circular anode 44. The fins 50 and 62 are also so dimensioned that their extreme edges 67 and 69 respectively are closely spaced from the peripheral flange 45 of the anode 44.

In accordance with the present invention, the fins 62 and 50 which are formed into a generally Y shaped con- 4 figuration, have a great contact area at this hot central portion. Thus, the local heating at the center of the anode is reduced by conducting the heat to outwardly cooler parts of the anode and to the fins 50 and 62 where it is dissipated by radiation, and to a lesser extent by conduction through the anode leads 46. This radiation cooling is further facilitated by sand blasting the fins 50 and 62 and the upper surface of the anode 44. According to actual tests, the anode temperature of a tube operating at maximum anode current, has been reduced by one hundred degrees centigrade with the benefit of the anode support assembly of the present invention.

The anode leads 46 are welded to opposite sides of the fin 5th at the bend between the central fin portion 55 and the outer fin portions 56. The leads 46 extend downward a portion of the distance along the jfin 50, approximately one-half the distance from the upper edge of the fin 50 to the anode 44 to be spaced from the anode 44. Because they are welded to the upper half of the fin 50, where it is relatively cool, the anode lead welds and the glass press are not highly stressed, which prevents the welds and glass press 48 from becoming impaired. An assembly, according to this invention offers a large radiating area, and with the tips of the fins disposed at points approximately one hundred and twenty degrees apart around the anode 44, it has a maximum radiation area for a three fin radiator. Although more than three extending fins may be utilized, any greater number would provide only a small increase in radiation area. For example, it four extending fins were provided there would be only a nine percent increase in radiation area without the effective warp suppression of the anode 44 according to this invention. If five fins were used, the warp suppression advantage would still be effective but it would only provide a thirteen percent greater radiation area. Also, the fact that the fins extend substantially radially of the anode 44 permits in- Iciuction heating of the anode without overheating the In manufacturing a tube according to the illustrated embodiment, it is merely necessary to bend the sheet metal blanks to form the fins 62 and 5t) and then join these plates together by spot welding. The fins 50 and 62 are then spot welded to the anode 44, and the entire assembly is weld-ed to the leads 46 so that the anode 44 is properly spaced from the grid shield 35. Although a two lead press 48 having the leads 46 fastened to the fin 50 is illustrated, any number of leads such as 46 fastened to the fins 50 and 62 could be used. However, some of the advantages are lost when only one lead is used. Although a nickel anode 44 is preferred, ity is apparent that the supporting structure is effective with an anode of any other suitable metal. It is apparent, that the height of the fins 50 and 62 may be varied in accordance with the requirements of the practice.

Thus, in summary, I have provided an improved anode assembly and supporting structure which effectively dissipates the heat from the hottest portion of the anode, prevents undulations and warping because of anode heat and is so constructed to prevent any breaking of the anode leadins or the glass press during operation.

Having described an improved anode support assembly for an electron discharge tube in accordance with one specific embodiment, it is understood that various modifications and adaptations may be made without departing from the spirit or scope of the present invention.

What I claim is:

1. A supporting assembly for a flat generally circular sheet metal anode of an electron discharge tube comprising a plurality of radially extending fins positioned angularly with respect to each other so that their extreme outer edges are approximately equi-angularly spaced, means fastening each of said fins adjacent one edge to the anode to be in intimate contact with the flat portion thereof,

said fins being so dimensioned and positioned relative to said anode so that the outer edges are substantially equally spaced from the peripheral edge of the anode and an inner edge of at least one fin is in registery and in intimate contact with the center point of said anode, and a pair of elongate rods spacedly fastened to one of said fins and spaced from the anode to hold the anode rigidly in a predetermined position in the tube.

2. An electrode assembly for a discharge tube comprising a fiat generally circular sheet metal anode, a sheet metal fin portion positioned on said anode to engage adjacent the center portion of said anode and be in intimate engagement therewith, a pair of angularly extending fin portions extending outwardly from opposite edges of said first named fin portion and in intimate engagement with said anode, another fin having one edge in intimate engagement with said first named fin portion at a point adjacent the center of said anode and in intimate engagement with said anode to extend outwardly from the anguiarly extending fins so that the extreme edges of said fins are approximately equidistant angularly from each other, whereby the heat from the center of the anode is conducted radially from the center of said anode and said fins prevent warping of said anode when heated.

3. An electrode assembly for a discharge tube, comprising a fiat generally circular sheet metal anode having a peripheral flange, a first sheet metal fin having a central portion and opposite end portions bent at an angle to said central portion, each said end portion extending outwardly from said central portion to form an inside angle in the order of one hundred and thirty-five degrees with the plane of said central portion, said first fin having a flange extending normal to the planes thereof, a second sheet metal fin having a first flange along one edge extending normal to the plane thereof and having a second flange along an adjacent edge extending normal to the plane of said second fin and said first flange, means intimately attaching the first flange of said second fin to the central portion of said first fin intermediate its opposite ends so that said second fin extends outwardly substantially normal to the plane of said central portion in a direction opposite from said extending end portions, means intimately attaching the flange of said first fin and the second flange of said second fin to said anode so that the point of juncture between said first and second fins is approximately at the center of said anode, and means rigidly attached to said first fin to hold the anode in a predetermined position in the discharge tube.

4. An anode assembly for an electron tube, comprising a plurality of joined sheet metal fins extending outwardly from a juncture point to have outer edges substantially equiangularly spaced from each other, a sheet metal anode including a fiat surface, means intimately attaching all said fins at one edge to the fiat surface of said anode in a position so that the point of juncture of said fins is adjacent and in intimate contact With the center of said anode, and supporting means rigidly attached to said fins spaced from said anode to support said anode in the tube.

5. An assembly according to claim 4 wherein said fins have a flange along adjacent edges, and said attaching means is a plurality of closely spaced spot welds securing said flange to the anode.

6. An assembly according to claim 4 wherein said supporting means is a pair of spaced rods attached at spaced points to said fin adjacent the center of the anode.

References ited by the Examiner UNITED STATES PATENTS 1,976,385 10/1934 Bruijnes 313- 2,951,960 9/1960 Watrous 313-42 X 2,980,800 4/1961 Steen 31342 X GEORGE N. WESTBY, Primary Examiner.

RALPH G. NILSON, Examiner, 

4. AN ANODE ASSEMBLY FOR AN ELECTRON TUBE, COMPRISING A PLURALITY OF JOINED SHEET METAL FINS EXTENDING OUTWARDLY FROM A JUNCTURE POINT TO HAVE OUTER EDGES SUBSTANTIALLY EQUIANGULARLY SPACED FROM EACH OTHER, A SHEET METAL ANODE INCLUDING A FLAT SURFACE, MEANS INTIMATELY ATTACHING ALL SAID FINS AT ONE EDGE TO THE FLAT SURFACE OF SAID ANODE IN A POSITION SO THAT THE POINT OF JUNCTURE OF SAID FINS IS ADJACENT AND IN INTIMATE CONTACT WITH THE CENTER OF SAID ANODE, AND SUPPORTING MEANS RIGIDLY ATTACHED TO SAID FINS SPACED FROM SAID ANODE TO SUPPORT SAID ANODE IN THE TUBE. 